This invention relates to coating compositions based on acid-neutralised amine- functional (meth)acrylic copolymers (the term "(meth)acrylic" here and below means "methacrylic and/or acrylic"), which are in particular suitable for lacier coating plastic components used in automotive construction.
DE-A-41 15 588 describes a process for priming plastic substrates using a solvent-based coating composition. The binder of this coating composition is based upon a (meth)acrylic copolymer crosslinked with epoxy resin or polyisocyanate, which copolymer may optionally contain tertiary amine groups. A disadvantage of this coating composition is that it contains an organic solvent.
Aqueous, two-component coating compositions based on hydroxy-functional amine-neutralised (meth)acrylic copolymers, which are crosslinked with polyisocyanate, are for example described in DE-A-38 29 587. These coating compositions are in need of improvement in terms of their adhesion characteristics, in particular to plastic substrates.
The as yet unpublished German patent application P 43 17 791 describes aqueous, two-component coating compositions based on oligomeric or polymeric polyols with the most varied binders and special hydrophobised polyisocyanate crosslinking agents. The polyols may have an acid value or an amine value. Acetic acid and formic acid are stated as the neutralising agents for amine-functionalised polyols. These coating compositions are preferably used as a water-based clear lacquer. They are in need of improvement in terms of their adhesion to plastic components.
The as yet unpublished German patent application P 42 29 982 describes aqueous, two-component coating compositions suitable for lacquer coating plastics, which compositions are based on cationically or preferably anionically stabilised polyols as the binder and which are crosslinked with polyisocyanate. No statement is made here as to the nature of the neutralising agent used. The coating compositions must contain chlorinated polyolefin as coupling agent and are distinguished by a relatively high content of 5 to 40 wt.% of aromatic solvent. Lacquer coating stressed plastic mouldings with coating compositions having an elevated content of aggressive solvents, such as for example aromatics, is problematic as it may lead to destruction of the plastic component.
DE-A-42 03 510 describes aqueous coating compositions prepared from a combination of a) a polyol component dissolved or dispersed in water, which may be present together with a reactive diluent, and b) a polyisocyanate component emulsified therein. Component a) here has chemically incorporated ammonium groups. These coating compositions are intended to have a long pot life.